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  26 <a name="boost.proto.functional.first"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Struct first</span></h2>
  29 <p>boost::proto::functional::first &#8212;
  30             A <a class="link" href="../../../PolymorphicFunctionObject.html" title="Concept PolymorphicFunctionObject">PolymorphicFunctionObject</a> type that returns
  31             the first element of a <code class="computeroutput">std::pair&lt;&gt;</code>.
  32           </p>
  33 </div>
  34 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  35 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../../proto/reference.html#header.boost.proto.functional.std.utility_hpp" title="Header &lt;boost/proto/functional/std/utility.hpp&gt;">boost/proto/functional/std/utility.hpp</a>&gt;
  36
  37 </span>
  38 <span class="keyword">struct</span> <a class="link" href="first.html" title="Struct first">first</a> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="../callable.html" title="Struct callable">proto::callable</a> <span class="special">{</span>
  39   <span class="comment">// member classes/structs/unions</span>
  40   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> This<span class="special">,</span> <span class="keyword">typename</span> Pair<span class="special">&gt;</span>
  41   <span class="keyword">struct</span> <a class="link" href="first/result_This_P_idp208615600.html" title="Struct template result&lt;This(Pair)&gt;">result</a><span class="special">&lt;</span><span class="identifier">This</span><span class="special">(</span><span class="identifier">Pair</span><span class="special">)</span><span class="special">&gt;</span> <span class="special">{</span>
  42     <span class="comment">// types</span>
  43     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">::</span><span class="identifier">first_type</span> <a class="link" href="first/result_This_P_idp208615600.html#boost.proto.functional.first.result_This(P_idp208615600.type"><span class="identifier">type</span></a><span class="special">;</span>
  44   <span class="special">}</span><span class="special">;</span>
  45   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> This<span class="special">,</span> <span class="keyword">typename</span> Pair<span class="special">&gt;</span>
  46   <span class="keyword">struct</span> <a class="link" href="first/result_This_P_idp208619920.html" title="Struct template result&lt;This(Pair &amp;)&gt;">result</a><span class="special">&lt;</span><span class="identifier">This</span><span class="special">(</span><span class="identifier">Pair</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">&gt;</span> <span class="special">{</span>
  47     <span class="comment">// types</span>
  48     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">::</span><span class="identifier">first_type</span> <span class="special">&amp;</span> <a class="link" href="first/result_This_P_idp208619920.html#boost.proto.functional.first.result_This(P_idp208619920.type"><span class="identifier">type</span></a><span class="special">;</span>
  49   <span class="special">}</span><span class="special">;</span>
  50   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> This<span class="special">,</span> <span class="keyword">typename</span> Pair<span class="special">&gt;</span>
  51   <span class="keyword">struct</span> <a class="link" href="first/result_This_P_idp208624240.html" title="Struct template result&lt;This(Pair const &amp;)&gt;">result</a><span class="special">&lt;</span><span class="identifier">This</span><span class="special">(</span><span class="identifier">Pair</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">&gt;</span> <span class="special">{</span>
  52     <span class="comment">// types</span>
  53     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">::</span><span class="identifier">first_type</span> <span class="keyword">const</span> <span class="special">&amp;</span> <a class="link" href="first/result_This_P_idp208624240.html#boost.proto.functional.first.result_This(P_idp208624240.type"><span class="identifier">type</span></a><span class="special">;</span>
  54   <span class="special">}</span><span class="special">;</span>
  55
  56   <span class="comment">// <a class="link" href="first.html#idp208628560-bb">public member functions</a></span>
  57   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Pair<span class="special">&gt;</span> <span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">::</span><span class="identifier">first_type</span> <span class="special">&amp;</span> <a class="link" href="first.html#idp208629120-bb"><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span></a><span class="special">(</span><span class="identifier">Pair</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  58   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Pair<span class="special">&gt;</span>
  59     <span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">::</span><span class="identifier">first_type</span> <span class="keyword">const</span> <span class="special">&amp;</span> <a class="link" href="first.html#idp208634048-bb"><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span></a><span class="special">(</span><span class="identifier">Pair</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  60 <span class="special">}</span><span class="special">;</span></pre></div>
  61 <div class="refsect1">
  62 <a name="idp373548656"></a><h2>Description</h2>
  63 <p>
  64               A <a class="link" href="../../../PolymorphicFunctionObject.html" title="Concept PolymorphicFunctionObject">PolymorphicFunctionObject</a> type that returns
  65               the first element of a <code class="computeroutput">std::pair&lt;&gt;</code>.</p>
  66 <div class="refsect2">
  67 <a name="idp373551152"></a><h3>
  68 <a name="idp208628560-bb"></a><code class="computeroutput">first</code> public member functions</h3>
  69 <div class="orderedlist"><ol class="orderedlist" type="1">
  70 <li class="listitem">
  71 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Pair<span class="special">&gt;</span>
  72   <span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">::</span><span class="identifier">first_type</span> <span class="special">&amp;</span> <a name="idp208629120-bb"></a><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span><span class="special">(</span><span class="identifier">Pair</span> <span class="special">&amp;</span> pair<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
  73 <div class="variablelist"><table border="0" class="variablelist compact">
  74 <colgroup>
  75 <col align="left" valign="top">
  76 <col>
  77 </colgroup>
  78 <tbody><tr>
  79 <td><p><span class="term">Returns:</span></p></td>
  80 <td><p>
  81                   <code class="computeroutput">pair.first</code>
  82                 </p></td>
  83 </tr></tbody>
  84 </table></div>
  85 </li>
  86 <li class="listitem">
  87 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Pair<span class="special">&gt;</span>
  88   <span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">::</span><span class="identifier">first_type</span> <span class="keyword">const</span> <span class="special">&amp;</span> <a name="idp208634048-bb"></a><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span><span class="special">(</span><span class="identifier">Pair</span> <span class="keyword">const</span> <span class="special">&amp;</span> pair<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
  89 <div class="variablelist"><table border="0" class="variablelist compact">
  90 <colgroup>
  91 <col align="left" valign="top">
  92 <col>
  93 </colgroup>
  94 <tbody><tr>
  95 <td><p><span class="term">Returns:</span></p></td>
  96 <td><p>
  97                   <code class="computeroutput">pair.first</code>
  98                 </p></td>
  99 </tr></tbody>
 100 </table></div>
 101 </li>
 102 </ol></div>
 103 </div>
 104 </div>
 105 </div>
 106 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 107 <td align="left"></td>
 108 <td align="right"><div class="copyright-footer">Copyright &#169; 2008 Eric Niebler<p>
 109         Distributed under the Boost Software License, Version 1.0. (See accompanying
 110         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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